Radical block copolymer thermally stabilized by a sulfur containing amino acid

ABSTRACT

Radial block copolymers of a monovinyl-substituted aromatic compound and a conjugated diene are rendered stable against melt flow drop off by the addition thereto of a stabilizer system which comprises (a) a hindered phenol (b) an organic phosphite and (c) a nitrogen containing compound.

nite States Patent Foclor Jan. 7, 1975 [5 RADICAL BLOCK COPOLYMER 3,629,372 12/1971 Drake 260/880 B THERMALLY STABILIZED BY A SULFUR 3,639,517 2/l972 Kitchen et al. 260/879 3,742,032 6/1973 Beears 260/4585 N 3,344,205 3,624,029 ll/l97l CONTAINING AMINO ACID Inventor: Lawrence M. Fodor, Bartlesville,

Okla.

Assignee: Phillips Petroleum Company, Bartlesville, Okla.

Filed: Mar. 19, 1973 Appl. No.: 342,531

us. c1.... 260/45.85 A, 252/402, 260/4585 N,

260/880 B 1m. (:1 C08g 51/60 Field 61 Search... 260/4585 A, 45.85 N, 880 B References Cited UNITED STATES PATENTS 9/1967 Grey et al. 260/880 B lnagemi et al. 260/459 R OTHER PUBLlCATlONS Chemical Abstracts, Vol. 73: l6462(v) Polybutene Coatings for Protecting Fruit," by Komiya Yasuhira. Chemical Abstracts, Vol. 64: 8853(d) Effect of Sulfur Amino Acids on Autoxidation of Edible Oils." by Z. Kwapniewski et al.

Primary ExaminerMelvyn l. Marquis Assistant Examiner-Gary R. Marshall [57] ABSTRACT Radial block copolymers of a monovinyl-substituted aromatic compound and a conjugated diene are rendered stable against melt flow drop off by the addition thereto of a stabilizer system which comprises (a) a hindered phenol (b) an organic phosphite and (c) a nitrogen containing compound.

8 Claims, No Drawings RADICAL BLOCK COPOLYMIER TI-IERMALLY on STABILIZED BY A SULFUR CONTAINING AMINO ACID R R BACKGROUND OF THE INVENTION 5 R R This invention relates to the stabilization of radial R block copolymers of a monovinyl-substituted aromatic compound and a conjugated diene.

Radial block copolymers of a monovinyl-substituted aromatic compound and a conjugated diene such as styrene and butadiene are known in the art, and are wherein R is H or an alkyl, cycloalkyl or aralkyl radical having from 1-20 carbon atoms, at least one R ortho to the OH being a radical having at least 3 carbon atoms and where, additionally, one R is a radical of the useful for a variety of purposes. However, for some apformula OH OH OH 2 R R- R R R R R R R R- R R plications it is desirable that the polymer be rendered more stable against thermally induced degradation. It is known to add a variety of different types of stabilizers to various types of polymers to protect same against deterioration. Nevertheless, in some instances radial block copolymers stabilized with conventional systems exhibit a particular type of deterioration which is evidenced by drop off in melt flow on heating for extended wherein R is as defined hereinabove and R is an alkylene group having l-l2 carbon atoms or an alkylidene group having 2*12 carbon atoms. Exemplary of these sterically hindered phenols are: 2,6-di-t-butyl-4-methylphenol 2,6-diisopropyl-4-methylphenol 2,4,6-tri-t-butylphenol 2,6-dicyclohexyl-phenol times, such as may be encountered in conventional fab- -t-0 tyl-4-m thy ph ol rication operations involving extrusion and the like. 2.6-diis p 0py y p n l 2,6-di-t-butyl-4-octadecylphenol SUMMARY OF THE INVENTION 2,6-di v l-methylbenzyl)-4-methylphenol It is an object of this invention to provide stable ra- 2- y y y p dial block copolymer composition; y y Y P It is another object of this invention to avoidmelt o y y P flow drop off of radial block copolymer which is suby P jected to extended thermal history; and p p p It is a further object of this invention to provide a sta- 40 f yy f y p l bilizer system of exceptional effectiveness utilizing y y non-toxic components. p py p In accordance with this invention, a resinous radial y P block copolymer of a monovinyl-substituted aromatic z'nonylphenol compound and a conjugated diene is rendered stable z'dodecylphenol against degradation by (a) a sterically hindered phenol z'teltradecylphen9l (b) an organic phosphite and (c) a nitrogen containing iy bfzt6'dflsopropylphenol) compound 2,2 -ethyl1dene b1s(4,6-di-tert-octylphenol) 4,4-butylidene bis(6-tert-butyl-meta-cresol) DESCRIPTION OF THE PREFERRED 4,4'-( l-methyl-propylidene)-bis--(2-tert-butyl-5- EMBODIMENTS methylphenol) As used herein the term sterically hindered phenol 44flsopropylldene blzdl'tert'butylphenol) includes a phenol of the formula: 'lsopropyhdene methylbenzyl)phenol] OH 4,4'-methylene bis[2-tert-butyl-6-(amethylbenzyl)phenol] R R 2,2'-methylene bis(4-methyl-o-tert-butylphenol) As used herein, the term organic phosphite includes H H phosphites represented by the following formula:

. v /0 Rs wherein R is H or an alkyl, cycloalkyl, or aralkyl radical, Q R3 or mixtures thereof containing 3-20 carbon atoms, no 7 more than one R being H and R is H or an alkyl, cycloalkyl, or aralkyl radical or mixtures thereof containing l-20 carbon atoms: 7

or an alkylene or alkylidine bisphenol of the formula wherein R is an alkyl, aryl, or cycloalkyl, radical containing l-l5 carbon atoms and combinations thereof. By this definition R would encompass a combination radical such as aralkyl, and alkaryl. The R radicals can be the same or different.

Exemplary of applicable phosphites are:

tri(nonylphenyl) phosphite triethyl phosphite triphenyl phosphite tri (2,4-dimethylphenyl) phosphite methyl diphenyl phosphite diisooctyl phenyl phosphite phenyl di (2-ethylhexyl) phosphite phenyl dicyclohexyl phosphite di (2-ethylcyclohexyl) n-butyl phosphite yclopq t l mn r dihexyl pho p i .7

2-phenylnonyl amyl dodecyl phosphite didecyl trimethyl phosphite The nitrogen containing compound can be either a urea compound or a sulfur containing amino acid as these two materials are defined hereinbelow.

The urea compound is represented by the following formula:

I I R R wherein each R can be the same or different and is H or an alkyl or cycloalkyl radical or combinations thereof containing 1-12 carbon atoms. Exemplary of these urea compounds are:

urea l-t-butylurea 1, l -dimethylurea 1,3-diethylurea l-cyclohexylurea l ,3-dicyclohexylurea l ,3-didodecylurea 1,1,3-trimethylurea 1,1,3 ,3-tet'ramethylurea The sulfur containing amino acid can be represented by the following formula:

wherein R is hydrogen, a 1-10 carbon atom hydrocarbon radical, or

R is an alkylene group having l-l0 carbon atoms; and M is hydrogen, -NH or a Periodic Group IA metal.

Preferred amino acids are cystine, cysteine, and methionine, all of which are naturally occurring amino acids which are non-toxic.

The resinous block copolymer composition of the invention must contain an effective stabilizing amount of the additives which in parts by weight of each component of the stabilizing system to be admixed with 100 parts per weight of the polymer is generally as follows: sterically hindered phenol 0.025 to 2, preferably 0.05 to 1; organic phosphite 0.25 to 5, preferably 0.5 to 2; and nitrogen containing compound 0.05 to 2, preferably 0.1 to 0.5. The total stabilizing system comprising all three components constitutes l to 6, preferably 1.5 to 5. The components can be mixed with the polymer separately or together by means of conventional practices known in the art such as by means of a roll mill, or the like.

Other additives such as UV stabilizers, fillers, lubricants, pigments, dyes and the like can be admixed with the compositions of the invention.

Radial block copolymer to be stabilized in accordance with the instant invention can be any resinous polymer having at least three vinyl-substituted aromatic compound/conjugated diene block copolymer chains radiating from a central nucleus. The word resinous is used herein in its conventional sense to denote a normally solid material not having elastic properties. Generally such materials will have a Shore D hardness (ASTM D 1706-61) of greater than 62, preferably greater than 69. Preparation of such radial polymers is broadly disclosed in Zelinski, et al., U.S. Pat. No. 3,281,383 issued Oct. 25, 1966, the disclosure of which is hereby incorporated by reference, it being understood that the radial block copolymers stabilized in accordance with this invention are limited to those having resinous characteristics. Resinous block copolymers having branches of polymer which demonstrate a plurality of modes on a gel permeation chromatograph curve prior to coupling as disclosed in Kitchen, et al., U.S. Pat. No. 3,639,517, the disclosure of which is hereby incorporated for a reference, are especially suitable.

The resinous radial block polymers stabilized in accordance with this invention can broadly be viewed as any radial conjugated diene/vinyl-substituted aromatic compound block copolymer prepared by first introducing. said vinyl-substituted aromatic compound in the presence of an organo-lithium initiator, thereafter adding said conjugated diene monomer to produce a block copolymer containing an active lithium atom on one end of the polymer chain as more fully described in said Zelinski, et al., patent. This lithium-terminated copolymer is then reacted with a compound which has at least three reactive sites capable of reacting with the lithiumcarbon bond and adding to the carbon possessing this bond in the polymer. The result is a polymer having relatively long branches which radiate from the nucleus .formed by the polyfunctional compound which is reacted with the lithium-terminated polymer. Preferred organolithium compounds can be represented by the formula: RLi, wherein R is a hydrocarbon radical seper molecule based on the total weight of the resinous block copolymer. Preferably the copolymers contain a weight ratio of styrene to butadiene within the range of :25 to :15. The polymer preferably has a melt flow in the range of about 0.5 to 20.0 grams/10 min. as determined by ASTM D l238-65T, condition G. The block copolymer'branches can be uniform in molecular weight distribution within the branches or have a polymodal distribution by charging the monovinylsubstituted aromatic hydrocarbon monomer in a plurality of increments as described in said Kitchen, et al., patent referred to hereinabove.

The thus stabilized composition can be worked into the desired shape by milling, calendaring, extrusion, injection molding or the like and will exhibit considerably improved resistance to reduction in melt flow during the processing.

EXAMPLE 1 (phr) and 0.5 phr 2,6-ditertiary-butyl-4-methylpheno1 plus urea (NH CONH in the amounts indicated. The compositions were held at 230 C for the times indicated and melt flow determined.

Urea

Melt Flow at 230C and 5 kg. (phr) 5 min. 10 min. 20 min.

Control Run 1 Control Run 2 Control Run 3 Control Run 4 l l l 1 ma m As can be seen the runs of the invention exhibited resistance to melt flow drop off.

EXAMPLE ll Polymer made according to the same recipe as that used in Example 1 was tested in an identical manner. All of the compositions in the following table contained 1.5 phr tris nonylphenylphosphite and 0.5 phr 2,6- ditertiary butyl-4-methyl phenol, plus the indicated additive. Results were as follows I claim:

1. A composition stabilized against melt flow drop off comprising: a resinous radial block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene, said copolymer comprising 70-95 weight percent of said monovinyl-substituted aromatic compound having incorporated therein an effective stabilizing amount of (a) 0.025 to 2 parts by weight per 100 parts by weight of said copolymer of a sterically hindered phenol, (b) 0.25 to 5 parts by weight per 100 parts by weight of said copolymer of an organic phosphite, and (c) 0.05 to 2 parts by weight per 100 parts by weight of said copolymer of a sulfur containing amino acid having the formula wherein R is hydrogen, a 1-10 carbon atom hydrocarbon radical or R is an alkylene group having 1-10 carbon atoms, and M is hydrogen, NH or a periodic Group IA metal.

2. A composition according to claim 1 wherein said amino acid is cystine, cysteine, or methionine.

3. A composition according to claim 2 wherein said hindered phenol is present in an amount within the range of 0.05 to 1 parts per hundred parts by weight of polymer, said organic phosphite is present in an amount within the range of 0.5 to 2 parts per hundred parts by weight of polymer and said amino acid is present in an amount within the range of 0.1 to 0.5 parts per hundred parts by weight polymer, and wherein said polymer is a 'styrene/butadiene polymer having a weight ratio of styrene2butadiene within the range of 75:25 to 85:15.

4. A composition according to claim 2 wherein said resinous radial polymer is a styrene/butadiene polymer having a weight ratio of styrene to butadiene within the range of 75:25 to 85zl5.

This represents a spurious result due possibly to failure to incorporate an additive.

The cysteine was added in a concentration of 0.10 grams per cc in water. The cystine was added in a concentration of 0.10 grams per cc in water as the disodium salt. The methionine was added in a concentration 0.10 grams per cc in water as the sodium salt.

While this invention has been described in detail for the purpose of illustration, it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope thereof.

5. A composition according to claim 4 wherein said hindered phenol is 2,6-ditertiary-butyl-4-methylphenol and said phosphite is tris(nonylphenyl) phosphite.

6. A composition according to claim 5 wherein said amino acid is cystine.

7. A composition according to claim 5 wherein said amino acid is cysteine.

8. A composition according to claim 5 wherein said amino acid is methionine.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3,859,250

DATED I January 7, 1975 NVENTORtS :Lawrence M. .Fodor It t5 certified that errortappears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cover page, first line of title of patent, first word, change "RADICAL" to RADIAL Page 1, column 1, first line of title of patent, first word, change "RADICAL" to RADIAL Signed and sealed this 27th day of Mayl975.

(SEAL) Attest:

C. MARSHALL DANN v RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT -3,859,?50

DATED January 7, 1975 iNvENTORrbi Lawrence M. Fodor It rs certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cover page, first line of title of patent, first word, change "RADICAL" to RADIAL Page 1, column 1, first line of title of patent, first word, change "RADICAL" to RADIAL Signed and sealed this 27th day of May 1975.

(SEAL) Attest:

C MARSHALL DANN r RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A COMPOSITION STABILIZED AGAINST MELT FLOW DROP OFF COMPRISING: A RESINOUS RADIAL BLOCK COPOLYMER OF A MONOVINYLSUBSTITUTED AROMATIC COMPOUND AND A CONJUGATED DIENE, SAID COPOLYMER COMPRISING 70-95 WEIGHT PERCENT OF SAID MONOVINYL-SUBSTITUTED AROMATIC COMPOUND HAVING INCORPORATED THEREIN AN EFFECTIVE STABILIZING AMOUNT OF (A) 0.025 TO 2 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID COPOLYMER OF A STERICALLY HINDERED PHENOL, (B) 0.25 TO 5 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID COPOLYMER OF AN ORGANIC PHOSPHITE, AND (C) 0.05 TO 2 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID COPOLYMER OF A SULFUR CONTAINING AMINO ACID HAVING THE FORMULA
 2. A composition according to claim 1 wherein said amino acid is cystine, cysteine, or methionine.
 3. A composition according to claim 2 wherein said hindered phenol is present in an amount within the range of 0.05 to 1 parts per hundred parts by weight of polymer, said organic phosphite is present in an amount within the range of 0.5 to 2 parts per hundred parts by weight of polymer and said amino acid is present in an amount within the range of 0.1 to 0.5 parts per hundred parts by weight polymer, and wherein said polymer is a styrene/butadiene polymer having a weight ratio of styrene: butadiene within the range of 75:25 to 85:15.
 4. A composition according to claim 2 wherein said resinous radial polymer is a styrene/butadiene polymer having a weight ratio of styrene to butadiene within the range of 75:25 to 85:15.
 5. A composition according to claim 4 wherein said hindered phenol is 2,6-ditertiary-butyl-4-methylphenol and said phosphite is tris(nonylphenyl) phosphite.
 6. A composition according to claim 5 wherein said amino acid is cystine.
 7. A composition according to claim 5 wherein said amino acid is cysteine.
 8. A composition according to claim 5 wherein said amino acid is methionine. 